3 answers

'Notify BPD 944 of notification' is a special kind of Event Manager task that is created each time there is a need to move token from one activity to another in a specific BPD instance.

So, basically each BPD token progression is a BPD task in the EM (BPD notification task that you can observe in EM Monitor in Process Admin console whenever token is progressed from one activity to another).
By default, every time IBM BPM asks the EM to do work (UCA, bpd notification to advance a token, etc), it forces the EM to reload its queues from the db and do work immediately.

These tasks should be executed quickly by EM. If you see millions of these tasks stuck in EM then you likely had a looping process and you might want to find those instances in question and perform a cleanup.

The 'Notify BPD 944 of notification' is a record of work from an instance, thus bpd_instance_id is 944. When you review the history you will see this for every task on the bpd. You can look up the BPD record in the process inspector to find more details about the instance and application it came from.